Fan and fan blower



Jan. 11 1927. E. VAN TO'FF FAN AND FAN BLOWER Filed Jan. 12, 1925 I2 2. A3 39 34- II g 24- lflvenl'or:

Ernest l a n 72f Patented 11, 1927. 1

UNITED sTAT'Es' mnsr vanrorr, or cmcaeo, rumors.

FAN Am) "rm BLOWER.

Application aieu nuar ia iim. serial No. 1.835.

the motor or pulley, and are discharged radially from the fan into a spiral housing for the blower.

The prime object of my invention broadly stated, is to provide a motor or pulley-driven fan-blower with means "adapted for substantially reducing, and to a minimum, as nearly as may be, losses in power and of air .heretofo're attributable to the axial location of its driving motor or ulley, losses due to the axial and radial ischarge of the air. currents through and from the fan, preventing the recirculation of the airfrom the rear to the front of the fan and accordingly cutting down its efliciency, and to prevent further losses of both power and air in a fan-blower through which the air currents are spirally conducted. i f

This invention also .relates toimproveo ments in fans and fan-blowers generally, in

fan structure occurs which the critical or chattering speed of a during its working speeds. p

More specifically stated, the object (if my invention is to provide a fan driven by an axially located electric motor or driving pulley, with means ada ted to isolate the air currents supplied to t 1e fan from contact therewith, and for directing said, air currents axially through and from the fan and into a collector, through and from which latter said air currents are discharged in afpproxlmately paths extending along lines at a right angle to the axis collector.

Still further objects of my invention are to provide an axially located driving motor for a fan or blower with means for directing to all of its parts currents of cooling air free the fan and .from dust and other materials liable to injure such parts; to utilize the air currents induced by the rotation of the fan for accelcrating the discharge of these cooling air currents without obstructing or retarding the air currents through and passing from the fan; and to have the fan structure so E T F'FlCE.-

constructed and arranged that the same site i .or dimensions of its componentfparts is. ca-

pable of being assembled and used to produce a fan delivermg air currents 'ata low pres-- sure, or a blower delivering currents of air at a lugh pressure, by changing the curvature'or shape of the vanes and the angle at which they are set with regard to their axis of rotation.

A further and important object of my invention is to provide a novel means ada ted for shifting with certainty any critica or chattermg speed awav from the predetermined best running speed and speeds of a power-driven fan or blower.

.With these ends in view, my inventionfinds embodiment in certain features of novelty in :theconstruction, combination and arrangement of parts by which the said ohjects and certain other objects. are attained, I

all as hereinafter fully, described with refers ence to the accompanying drawings and more fully pointed out in the claims.

In said drawings,

Fig. 1 illustrates a longitudinal section 0L a fan"- blower in which my invention finds embodiment.

Fig. 2, a transverse section taken on the line 2-201? F ig. 1'. a

Fig. 3 is a side elevationof a weighted vane.

vane, and

Fig. 5 diagrammatically illustrates the i Fig. 4' is a longitudinal section such distortion of the shaft produced by critical. 1

speed.

S1m1lar characters of reference indicate the same parts in the several figures of the drawings.

6 indicates a shaft for driving the fan, which, as shown in the drawings, is driven by a motor 7, but may be by means ofa pulley (not shown) mounted thereon, on

one ,end of which shaft is keyed or otherwise secured a hub 8, havinga surrounding flange 9, adapted to support an inner ring 10,, se-.

cured thereto by bolts 11, whence it diverges towards its rear and open end, through which the air currents supplied thereto are discharged.

Mounted upon the ring 10 are vanes 12 secured thereto by rivets 13. Vanes 12 are surrounded by'and support an outer ring 14, secured thereto by means of rivets 15, which outer ring, together with the inner ring,

provides apassageybetween them for the air currents sup lied to and discharged from the fan and so that the supplied air currents enterin the fan diverge and accordingly disc arged from the fan. The fan thus constructed and the hub 8 are surrounded by a housing 16, open at both ends, and sufficiently separated from are the outer ring of the fan for the latter to and 16 will be drawn toward the larger end thereof making it impossible for air to enter at the larger end. 7

' Motor 7 is surrounded by a cylindrical jacket 17, the diameter of which is sufiicient to provide a substantially annular passage 18, through which to supply the motor with cooling air currents drawn into a chamber 19, located. between the closed end of the inner ring and the adjacent ends of the motor and the jacket 17, the inner end of which jacket 17, being of less diameter than the surrounding surface of the inner ring,-

provides a passage 20, through which the cooling air supplied to the chamber 19 is conducted to and supplements the currents discharged from the fan.

The motor 7 is mounted upon a base-plate 21, supported by diverging arms 22, 22, se-

cured by means of screws or bolts 23 to a flange 24, projecting from the fan housing p In operation it will now be seen that the currents of air passing through and discharging from the fan operate to produce a vacuum in the air passage 20 and the chamber 19 and the passage 18, surrounding the motor, which vacuum induces air currents to pass through the annular passage 18 to directly contact with the closed end of the inner ring and discharge thence around and between the end of the jacket 17 and the surrounding surface of the inner ring, and as a result of which the air discharging from the fan is accordingly supplemented with an additional amount of air which has before been utilized as a cooling medium for the motor.

. In this connection it is to be observed that the same results will be attributable to the substitution for the motor of a driving pulley located upon the shaft, within the jacket 17, upon the drive shaft, in which case, however, the shaft would be accordingly lengthened.

As shown in are each provided with a plain surface 29 and a concavo-convex surface 30, which Figs. 1 and 2, the vanes 12.

3 are. setup in the vanes plain surface is bounded the inner ring I 10 and a line drawn from the forward end of the outer ring to the inner edge of the inner ring, and with the result that the width of their concavo;convex surface is gradually increased and terminates at'the rear edge of the vanes.

-The plain surface 29 not only provides an unobstructed entrance for the air currents between the vanes, but for their uniform distribution throughout the length of their concave-convex surface which, gradually widens, as it does from the front edge to the rear edge of every vane.

The concavo-convcx surface of a portion of the vanes of a fan constitutes an important feature of my invention for increasing theefiiciency of a fan-blower, in that such a surface provides a means for collecting air currents and counteracting their centrifugal force before their discharge from the fan into the collector for a fan-blower, and for delivering the air currents at their destination with a force substantially and materially greater than would otherwise be possible.

As a'means, however, for regulating and controlling the volume of coolihg air supplied to the motor. or a driving pulley, without changing the speed of the fan, and particularly for the purposes of a fan-blower, the passage 18 surrounding the motor is in open communication with a chamber 31, closed at its outer end by a cap-plate 32, provided with a pipe 33, 'referably having a stop-cock or valve (not Shown).

For the purposes of a blower, the fan is provided, as shown in Fig. 1, with a collector 34 in open communication'with the fanand surrounding the flange 24 of the fan housing 16, to which it is secured by the screws 23 and 28, respectively securing the bracket arms 22 and the bars 26 to this flange, and provided with a conduit 35, projecting in a line at a right-angle to the axis of the collector and which may be cast therewith.

The form of this collector is that of an annulus, the inner walls 36 of which not only provide the wall for and'surrounding the chamber 31, but, as indicated at 37, are substantially semi-elliptical in cross-section for accordingly reducing the force of the impact of, and resistance to the air currents axially discharged from the fan in a vdirection toward the right as viewed in Fig. 1, and for deflecting and directing them towards and through the conduit 35.

In all power-operated fans, the vanes of which are secured to a hub revolved about a fixed axis, the forces of mass-acceleration due to the fast running of the fan, increase rapidly with the speed, namely, with the square of the number of revolutions of the fan,

and throughout the with the result thatvario us vibrations.

fan structure, which vibrations, when 'osed or balancing each other, are, not 0 ectionably injurious to the fan,.but which,

when in unison, as indicated by the chattering of tlie fan, are seriously injurious thereto at the speed 'at' which the fan is then running and until. the unison of these vibra tions is destroyed, agmay. be, either by increasing or diminish g the speed of the fan until sucli chattering ceases, and, if need be, until their opposition is restored.

The sound produced by this chattering of the fan, therefore, furnishes the evidence that the fan is then'running at, its critical speed, namely, a, speed producing vibrations in unison, or harmonic between themselves, which, ifcontinued, will seriously in jure the fan.

For instance, suppose the critical speeds of a fan occur when it is running at 400,

800, 1200 and 1600 revolutions per minute within its working range, and the fan is kept running at any one or more of these speeds, a lateral force, diagrammatically illustrated in Fig. 5, will be supplied to the driving .shaft, the effect of which is to subject the bearings and vanes to undue stresses, ultimately resultingfin loosening their rivets and scoring the hearings, which loosening of the rivets and scoring of the bearings is far more pronounced at 1200 revolutions per minute than at 400 revolutions per minute, as their square, namely nine times greater. In betweenthese critical speeds, it is, however, found that the fan runs quietly because the vibrations of the vanes and of the rotating aggregate counteract each other.

Although' it has long been well known that the critical speed of a rotating body 1s a function of its speed and mass, I am the first to discover that, by changing only the weight of the vanes without destroying their form, and in the absence of any necessity for disassembling the fan structure, the critical speed of a fan may be shifted away from .any speed and particularly from its best running speed;

Howcver carefully power-driven fans may be designed, their best working speed frequently coincides with their critical speed, and as a result of which the common practice has been torun such fans at a speed substantially less than their best working speed,-

I i and at about 100 or more revolutions per minute below their critical speed, ratherthan disassemble the fanstructure to chan e the form of its vanes, as must'be, for shi ting the critical speed away from'the best running speed for which thefan was originally designed.

In other words, when the best running speed of a fan coincides with its critical speed, and assuming, for example, that this occurs in the structure shown in Figs. 1 and 2, in which my invention finds embodiment,

and the remedy therefor in' the structure shown in Figs. 3 and 4, in which the vanes are provided with an additional weight, consisting of a metal plate 40, secured thereto by rivets {11, passing through such bar, the vanes 12, and; if need be, a reinforcing plate 42 for the rivet, which bar '40 extends across the surface of the vane adjacent its ends, and conforms thereto and is suificient in weight to increase the" momentum of the vanes to shift the critical speed away from the running speed of the fan, as before described, by setting upvibrations opposed to and destroying the unison of the vibrations [producing the critical speed, which before coincided with the running s eed of the fan.

In an ideally constructe and operated fan, the centers of gravity of all of the vanes will rotate in a plane perpendicular to their axis of rotation, as indicated in Fig. 5 bythe dotted line 5.

In practice, however, it is impossible to produce such a construction because of the occurrence of unavoidable discrepancies in the thickness, the shape, the curvature and variations in the smoothness of the surface of the vanes, and in their resulting diflerent resistances to the flow of the'air currents outer rings, between which'spaced vanes are located, regardless of whether said rings lie in a plane parallel to or extend at anangle with reference to the axis of rotation, and also whether or not the inner ring is closed at one end or open at. both ends; nor is my invention to be limited to the means herein described, by which the inner ring is connec'ted with and supported by the :driveshaft for the fan,

Furthermore, my invention is not to be limited to the special form of'collector for a fan constructed as above described, or other than isipointed out in the claims.

Having described my invention, what I 1am; and desire'to secure byLetters Patent 1. A fan-blower, comprising in combina tion an outer ring open at both ends, a housin surrounding said ring, an inner ring su stantially closed at its front end, a supporting drive shaft therefor extending axially therewith, a motor mounted upon said shaft, ajacket surrounding said motor providing a passage between the jacket and the motor, in open communication with the rear end of the fan, and a collector annular 1n form 1n open communication wlth the fan, the inner Walls of which surround and provide a passage for an air supply chamber leading tothe acket; said collector having a discharge radial to the axis of the fan.

2. The combination with a fan, of a housing surrounding said fan, said fan and housinghaving spaced diverging surfaces, the divergence extending toward the exhaust side of the fan.

3. A fan comprising a plurality of blades and having a critical speed, and means for increasing the weight of said blades for shifting said critical speed.

4. A 'fan comprising a rotatable member having blades, and a critical speed, means for shifting said critical speed by. varyingv the weight of said blades.

5. A fan comprising a rotating mass having a critical speed, and means for varyinn the weight of said mass for varying said critical speed.

6. A fan comprising an outer annulus, an inner annulus, and blades between said annuli, said blades having a flat portion adjacent the inner annulus and a convex surface above said flat portion.

7. A fan comprising an outervring, an inner ring, blades between said rings, said blades having a flat portion adjacent the inner ring which decreases toward the exhaust side of the fan, and a convex portion above said flat portion.

8. The combination 'with a fan, of a hous ing adjacently surrounding said fan, said housing and fan being so constructed that the centrifugalforce of the air currents between said fan and housing directs said currents toward the exhaust side of said fan.

I 9. 'In a fan blower, a fan having an inner ring closed at its front end, a housing surrounding said fan, a collector having a radial discharge attached to said housing, 

